Heat Exchange Means with an Elastocaloric Element, Which Surrounds a Fluid Line

ABSTRACT

A heat exchanger is configured to surround a fluid line which guides a heat transport fluid. The heat exchanger includes at least one elastocaloric element, which is connected to the fluid line, and at least one actuator, which acts on the elastocaloric element and is configured so as, when actuated, to exert a force on the at least one elastocaloric elements in order to deform the at least one elastocaloric element. The heat exchanger further includes at least one fastening element, which is configured to fasten the heat exchanger to the fluid line.

This application claims priority under 35 U.S.C. § 119 to application no. DE 10 2018 213 497.9, filed on Aug. 10, 2018 in Germany, the disclosure of which is incorporated herein by reference in its entirety.

The disclosure relates to a heat exchange means, which surrounds a fluid line, which guides a heat transport fluid, and comprises at least one elastocaloric element, at least one actuator and at least one fastening element. Furthermore, the disclosure relates to a heat exchange system, which comprises the fluid line, the at least one heat exchange means and an electronic control unit for controlling the at least one actuator.

BACKGROUND

The elastocaloric effect describes an adiabatic temperature change of a material if the material is subjected to a mechanical force and, for example, is deformed. By means of the mechanical force or the deformation, a conversion of the crystal structure, also called phase, is caused in the material. The phase conversion leads to an increase of the temperature of the material. If the heat liberated in the process is removed, the temperature is reduced and the entropy decreases. If the mechanical force is then taken away, a reverse phase conversion (conversion back) is caused in turn, leading to a reduction of the temperature of the material. If heat is then supplied again to the material, the entropy increases again.

After the approximately adiabatic phase conversion, the temperature lies above the starting temperature. The heat produced in the process can be removed, for example, to the environment and the material then adopts the ambient temperature. If the phase conversion back is now initiated, by the mechanical force being reduced to zero, a lower temperature than the starting temperature arises. Temperature differences between the maximum temperature after the phase conversion and minimum temperature after the conversion back (when heat is output previously) of up to 40° C. can be achieved.

Materials on which the elastocaloric effect can be demonstrated are referred to as elastocaloric materials. Such elastocaloric materials are, for example, shape memory alloys which have superelasticity. Superelastic alloys are distinguished in that they automatically return back again into their original shape even after severe deformation. Superelastic shape memory alloys have two different phases (crystal structures): austenite is the phase stable at room temperature, and martensite is stable at lower temperatures. A mechanical deformation causes a phase conversion from austenite to martensite, which results in an adiabatic rise in temperature. The increased temperature can now be output to the environment in the form of heat, which leads to a decrease in entropy. If the elastocaloric material is again relieved of load, a conversion back from martensite to austenite takes place and, in association therewith, an adiabatic reduction in temperature.

Elastocaloric elements which are composed of such elastocaloric materials are used for cooling and for heating. Use is typically made here of fluid lines which are filled with heat transport fluid and via which the heat is transported. More precisely, the heat transport fluid transports the heat from the component to be cooled toward the elastocaloric elements, or it transports the heat away from the elastocaloric elements and toward the component to be heated.

The elastocaloric elements are conventionally arranged in a central cooling or heating unit, from which the fluid lines emerge and then run to the components. Along the fluid lines, heat is exchanged with the environment, and therefore a heat loss is produced and the cooling or heating power reduced. The central units typically have a motor, generally an electric motor, in order to deform the elastocaloric elements.

SUMMARY

A heat exchange means is proposed, which is configured to surround a fluid line, which guides a heat transport fluid, e.g. a coolant/refrigerant. The heat exchange means comprises at least one elastocaloric element, at least one actuator, which acts on the at least one elastocaloric element, and at least one fastening element.

The at least one elastocaloric element can be connected here to the fluid line, is connected to the fluid line or can be arranged on the fluid line. There is a thermal connection here between the at least one elastocaloric element and the fluid line. The at least one elastocaloric element can be fastened directly to the fluid line or preferably can be held in the connection via the at least one fastening element.

The at least one actuator is configured so as, when the actuator is actuated, to exert a force on the at least one elastocaloric element. The actuator can be, for example, a piezo element, which expands and, in the process, exerts a pressure on the at least one elastocaloric element, or an electric actuator or a magnetic actuator, for example a solenoid.

The at least one fastening element is configured to fasten the heat exchange means to the fluid line. The at least one fastening element is preferably a cuff or a casing. The at least one fastening element is preferably connected to the at least one actuator and holds the latter. In other words, the at least one actuator is anchored on one side on the at least one fastening element. The at least one actuator is thereby fixed on one side and can exert a force on the at least one elastocaloric element without moving and accordingly deforming the at least one elastocaloric element.

The above-described arrangement of the elastocaloric elements directly on the fluid line provides the following advantages especially over conventional heat exchange devices, in which the elastocaloric elements are arranged in a central unit:

The heat exchange by means of the at least one elastocaloric element can take place directly on the fluid line. Accordingly, the heat can be supplied to the heat transport fluid or removed from the heat transport fluid directly at the required location, and only heat which is actually needed is transmitted. By means of the arrangement directly on the fluid line, the heat exchange means can be placed on the fluid line as close as possible to a consumer, as a result of which the heat loss of the heat transport fluid via the fluid line is significantly reduced because of the short distance between the heat exchange means and the consumer, and, accordingly, the efficiency of the heat exchange system can be increased.

Furthermore, the decentralized arrangement of the heat exchange means makes it possible to dispense with the central unit in which the elastocaloric elements are arranged. Such central units generally have a motor, for example an electric motor, which turns out to be significantly larger than the actuators of the heat exchange means. Said motor can be dispensed with, as a result of which the required construction space for a heat exchange system is reduced.

The at least one heat transport means is preferably arranged in sections of the fluid line in which the fluid line runs “rectilinearly”, i.e. has only a small curvature, if any at all, at least for the width of the heat transport means.

The at least one elastocaloric element, the at least one actuator and the at least one fastening element can advantageously each be designed in the form of an annular disk. In this configuration, the components mentioned can be arranged annularly around the generally tubular fluid line, and therefore the heat exchange means surrounds the fluid line. It should be noted that the annular disk can have an opening in its ring and/or an opening mechanism for its ring, in order to be able to open the annular disk during the installation on the fluid line. The annular fastening element can be designed, for example, in the form of a cuff which is placed around the fluid line and is then tightened.

In a preferred development of the heat exchange means, two actuators are arranged in the longitudinal direction of the fluid line next to one of the elastocaloric elements. The longitudinal direction of the fluid line is considered to be the longitudinal direction of the generally cylindrical pipe in the respective section of the fluid line, in other words the direction parallel to the direction of flow of the heat transport fluid. The elastocaloric element is arranged between the two actuators. In the case of annular components, the elastocaloric element is arranged between the end sides of the two actuators. If, when the actuators are actuated, the two actuators expand simultaneously in the longitudinal direction the two actuators each exert a force on the elastocaloric element, specifically from different sides. As a result, the elastocaloric element is deformed.

In addition, each of the two actuators can be connected to in each case one fastening element, which is arranged in the longitudinal direction of the fluid line. The fastening elements are connected here to the actuator on the side in each case opposite the elastocaloric element—the end side in the case of annular components. Each of the two actuators can be held by one of the fastening elements. Accordingly, the actuators are fixed on the fluid line via the fastening elements. If, when the actuators are actuated, the two actuators now expand simultaneously in the longitudinal direction, the expansion in the direction of the fastening elements is suppressed and the actuators expand only in the direction of the elastocaloric element, and therefore the two actuators each exert a force on the elastocaloric element.

Preferably, at least two actuators can divide a common fastening element. The common fastening element is connected to the at least two actuators and holds the latter simultaneously. Particularly preferably, precisely two actuators divide a common fastening element. For the above-mentioned case in which the actuators are connected in the longitudinal direction to the fastening element, it is advantageous for precisely one actuator to be connected to one side of the common fastening element transversely with respect to the longitudinal direction—therefore to an end side.

As already described, the at least one elastocaloric element is thermally connected to the fluid line. In order to improve this thermal connection, i.e. in order to increase the heat transfer via said thermal connection, a heat-conducting layer can be provided between the at least one elastocaloric element and the fluid line. The heat-conducting layer is advantageously designed in such a manner that it provides an increased contact surface on the fluid line and/or provides an increased contact surface on the at least one elastocaloric element, as a result of which a greater heat transfer can take place.

In contrast thereto, it is of advantage to thermally insulate the at least one actuator from the fluid line and from the at least one elastocaloric element. For this purpose, a heat-insulating layer can be provided between the at least one actuator and the at least one elastocaloric element and also between the at least one actuator and the fluid line. By means of said heat-insulating layer, no heat transfer can take place between the elastocaloric element and/or the heated or cooled heat transport fluid and the actuator. In addition, the heat-insulating layer can surround the outer side of the heat transport means, said outer side facing away from the fluid line, in particular the outer side of the elastocaloric elements, and therefore no heat transfer to the environment takes place. Accordingly, the heat-insulating layer provides the advantage of reducing the heat loss within the heat exchange means and the heat loss to the environment and therefore of increasing the efficiency.

Furthermore, a heat exchange system is proposed which comprises at least one of the above-described heat exchange means, the fluid line and an electronic control unit. As already described, the at least one heat exchange means is arranged on the fluid line. Furthermore, the electronic control unit is configured to control the at least one actuator of the at least one heat exchange means. The advantages of the heat exchange means can be taken on by the heat exchange system.

In an advantageous manner, a plurality of such heat exchange means are arranged on the fluid line. In this case, the electronic control unit is configured to control the at least one actuator of each of the plurality of means. The greater the number of heat exchange means arranged on the fluid line, the greater is the maximum possible heat flow.

Each heat transport means is preferably arranged in sections of the fluid line in which the fluid line runs “rectilinearly”, i.e. has only a small curvature, if any at all, at least for the width of the heat transport means.

In a particularly preferred refinement, the plurality of the heat exchange means are connected to one another in the manner of a cascade. That is to say, the heat exchange means are arranged lying on one another or at a small distance one behind another and act successively on the same fluid volume of the heat transport fluid. In addition, the control unit is preferably configured in such a manner that the actuators of the plurality of heat exchange means are controlled successively in terms of time depending on the flow properties of the heat transport fluid, and therefore the same fluid volume of the heat transport fluid is cooled or heated ever further from element to element within the cascade.

In addition, a reservoir in which the heat transport fluid is stored and at least one return line between the fluid line and the reservoir can be provided in the heat exchange system. By means of the at least one return line, the heat transport fluid is guided back from the end of the fluid line, and/or after it has flowed through the consumer, to the reservoir. On the other side, the heat transport fluid is supplied from the reservoir to the beginning of the fluid line.

Optionally or additionally, at least one internal return line which connects the end of the fluid line to the beginning of the fluid line can be provided without a consumer or a reservoir being arranged in-between. By means of the at least one internal return line, the heat transport fluid is conveyed back directly to the beginning of the fluid line without a detour or intermediate storage and without having flowed through the consumer. The at least one heat exchange means is arranged here between the beginning of the fluid line and the end of the fluid line.

In order to control the flow of the heat transport fluid, in particular if the return and/or the internal return is or are present, the heat exchange system has valves at least at the beginning of the fluid line and at the end of the fluid line.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the disclosure are illustrated in the drawings and explained in more detail in the description below.

FIG. 1 shows an isometric illustration of a heat exchange means according to a first embodiment of the disclosure with an elastocaloric element.

FIG. 2 shows a sectional illustration of the heat exchange means from FIG. 1.

FIG. 3 shows an isometric illustration of the heat exchange means according to a second embodiment of the disclosure with a plurality of elastocaloric elements.

FIG. 4 shows a schematic isometric illustration of part of a heat exchange system according to one embodiment of the disclosure with a plurality of heat exchange means according to the second embodiment from FIG. 3.

FIG. 5 shows a schematic illustration of the heat exchange system according to one embodiment.

DETAILED DESCRIPTION

FIGS. 1 and 2 each illustrate a first embodiment of a heat exchange means 100 according to the disclosure, wherein FIG. 1 shows an isometric view and FIG. 2 shows a sectional illustration. The heat exchange means 100 is arranged directly on a fluid line 3, through which a heat transport fluid flows, and surrounds said fluid line. The heat exchange means 100 comprises two actuators 1, for example piezo actuators, an elastocaloric element 2 which is composed of elastocaloric material, and two fastening elements 4. The actuators 1, the elastocaloric element 2 and the fastening means 4 are each designed in the form of annular disks which are arranged around the fluid line 3 and surround the latter. The elastocaloric element 2 is surrounded in the longitudinal direction of the fluid line 3 by the two actuators 1, and in each case one end surface of the elastocaloric element 2 lies on one of the end surfaces of in each case one actuator 1. The respectively other end surface of each actuator 1 is connected in the longitudinal direction to an end surface of in each case one fastening element 4, and therefore the actuators 1 are held by the fastening elements 4 (end surfaces cannot be seen in this illustration). In the present embodiment, the fastening elements 4 are designed as a casing for the fluid line 3 and are placed around the latter. In a further embodiment which is not shown here, the fastening elements 4 are designed as cuffs which are placed around the fluid line 3 and are then tightened. The actuators 1 and the elastocaloric element 2 here can also have openings in their ring and/or an opening mechanism for their ring in order to be able to open them during the installation on the fluid line 3. The heat exchange means 100 is therefore fastened to the fluid line 3 by means of the fastening elements 4, and the actuators 1 are fixed on one side in each case.

FIG. 2 shows the internal design of the heat exchange means 100. Identical components are identified by the same reference signs and the description thereof again is dispensed with. A heat-conducting layer 5, for example made of copper, is provided between the elastocaloric element 2 and the fluid line 3, via which layer the elastocaloric element 2 is thermally connected to the fluid line 3. By means of the heat-conducting layer 5, firstly the contact surface on the fluid line 3 is increased, in the example illustrated in FIG. 2 approximately to the size of the elastocaloric element 2 and of the two actuators 1 together, and also the contact surface on the elastocaloric element 2 is increased, in which contact surface the heat-conducting layer 5 approximately completely surrounds the elastocaloric element. Secondly, the heat transport is increased by the material properties of the heat-conducting layer 5. Furthermore, a heat-insulating layer 6 is provided which is arranged around the actuators and which thermally insulates the actuators 1 from the heat-conducting layer 5 and from the fluid line 3. In addition, the heat-insulating layer 6 is arranged over the complete outer side of the heat exchange means 100—the outer side is considered as being the outer circumferential surface of the components 1, 2, 4, i.e. the surface of said components 1, 2, 4 opposite the fluid line 3 and the end surfaces of the fastening elements 4 that are opposite the actuators 1—and therefore prevents a heat loss in relation to the environment.

In order to activate the actuators 1, an electronic control unit 8 is provided which is connected to a current/voltage supply 9 and controls the electric current from the current/voltage supply 9 via the current line 7 toward the actuators 1. If the actuators 1 are supplied with current, they expand simultaneously. Since the two actuators 1 are fixed on one side each by the fastening element 4, the actuators can expand only in the direction of the elastocaloric element 2, as a result of which they each exert a force from both sides on the elastocaloric element 2, by means of which force the elastocaloric element 2 is compressed and deformed in the process. Owing to the elastocaloric effect, the deformation of the elastocaloric element 2 generates heat which is output via the heat-conducting layer 5 to the fluid line 3 in which the heat transport fluid flowing therein is heated. Depending on whether a consumer (not shown here) is intended to be heated or cooled, the heat is guided to the consumer or transported away until the heat is completely removed from the elastocaloric element 2. If the two actuators 1 are now no longer supplied with current, they retract into their starting state, and therefore force is no longer exerted on the elastocaloric element 2 and the latter likewise deforms back. During the deformation back, the elastocaloric element 2 absorbs heat which is removed via the heat-conducting layer 5 from the heat transport fluid now flowing through the fluid line 3, as a result of which the heat transport fluid cools. Depending on the application, the cooled heat transport fluid is now removed or supplied to the consumer. The heating or cooling power can be controlled via the introduced electrical energy (current/voltage) which is converted by the actuator 1 into mechanical energy. The transporting away of the heat transport fluid and the control thereof will be described in detail in conjunction with FIG. 5, in which the heat exchange system according to the disclosure is described.

FIG. 3 shows an isometric view of a second embodiment of the heat exchange means 110 with a plurality of actuators 1, a plurality of elastocaloric elements 2 and a plurality of fastening elements 4. Also in the case of the first embodiment, a plurality of actuators 1, a plurality of elastocaloric elements 2 and a plurality of fastening elements 4 can be provided by a plurality of heat exchange means 100 being arranged one behind another in the longitudinal direction of the fluid line 3. In contrast thereto, in the case of the second embodiment, two inner actuators 1—i.e. the actuators which are not arranged first or last in the row—divide a common fastening element 4. That is to say, one end side of the fastening element 4 is connected to the one actuator 1 and the other end side of the fastening element 4 is connected to the other actuator 1, and therefore the fastening element 4 in this case holds the two actuators 1 and fixes same. The heating or cooling power can be varied by the number of heat exchange means 100, 110 used and activated.

FIG. 4 shows part of a heat exchange system according to an embodiment of the disclosure in an isometric illustration. A plurality of heat exchange means 110 according to the second embodiment are arranged as a cascade on the common fluid line 3. The heat transport means 110 are arranged in “rectilinear” sections of the fluid line 3 in which the fluid line 3 has only a small curvature, if any at all. The plurality of heat transport means 110 are controlled via the electric line 7 by the common control unit 8 and are supplied by the common current/voltage supply 9. The actuators 1 are activated successively in terms of time, specifically in such a manner that the elastocaloric elements 2 always act on the same fluid volume of the heat transport fluid flowing through the fluid line 3. For this purpose, the actuators 1 are activated sequentially depending on the time which a fluid volume which has already absorbed or output heat requires in order to reach the next elastocaloric element 2. Said time can be calculated from flow properties, such as the flow speed, and the distance between the elastocaloric elements 2, or determined empirically. By means of this activation, the fluid volume which has already absorbed or output heat is further heated or cooled by the next elastocaloric element 2. As a result, the fluid volume is heated or cooled ever further from element to element.

FIG. 5 shows a schematic illustration of the entire heat exchange system according to one embodiment of the disclosure. The plurality of heat exchange means 110 and the fluid line 3, and also the electronic control unit 8, the current/voltage supply 9 and the electric line 7 correspond to those which are shown in FIG. 4 and to the description of which reference is made. In addition to the components which have already been described, this figure illustrates a reservoir 11, in which the heat transport fluid is stored, the consumer 17 and a feed pump 18 and also further lines 12, 13, 14, 15, 16, 19, return feed pumps 20 and valves 10, 21, which control the flow of the heat transport fluid. The valves 10 are arranged at the end of the fluid line 3 and the valves 21 at the beginning of the fluid line 3, the valves 10, 21 being designed as multi-way valves.

In order to provide a better description, it is assumed below that the consumer 17 is intended to be cooled. The heat transport fluid is conveyed out of the reservoir 11 by the feed pump 18 via the inflow line 19 to the fluid line 3. In the fluid line 3, the heat exchange means 110 act on the heat transport fluid in the manner already described in detail above. The heat transport fluid (volume) heated by the elastocaloric elements 2 is guided back directly to the reservoir 11 by a first outflow line 14 via the valves 10 without passing through the consumer. Accordingly, the first outflow line corresponds to a return line to the reservoir 11. Subsequently, the valves 10 are switched over and the heat transport fluid (volume) cooled subsequently by the elastocaloric elements 2 is conducted by a second outflow line 15 to the consumer 17 where it absorbs the heat from the consumer 17. In order to keep the heat loss low, the second outflow line 15 between the end of the fluid line 3 with the heat exchange means and the consumer 17 is kept as small as possible. The heat transport fluid is subsequently guided back via a further return line 16 to the reservoir 11. In the reservoir 11, the heated heat transport fluid and the heat transport fluid supplied to the consumer 17 are mixed.

In the event that the heat transport fluid is intended to be cooled further before it is conducted to the consumer 17 and to the reservoir 11, internal return lines 12, 13 are provided between the valves 10 and 21. Return feed pumps 20 are provided within the internal return lines 12, 13, said return feed pumps conveying the heat transport fluid back, after the latter has flowed through the fluid line 3 and been cooled by the elastocaloric elements 2, from the valves 10 at the end of the fluid line 3 to the valves 21 at the beginning of the fluid line 3 without said heat transport fluid flowing through the consumer 17 and/or the reservoir 11. The cooled heat transport fluid can now flow once again through the fluid line 3, where it is cooled again by the elastocaloric elements 2. In this exemplary embodiment, two internal return lines 12 and 13 are provided, wherein the cooled heat transport fluid flows via the one return line and the heated heat transport fluid via the other.

The same heat exchange system can also be used to heat the consumer. For this purpose, in the event of the activation described above, only the heated heat transport fluid has to be conducted to the consumer 17 where it outputs the heat to the consumer 17, and the cooled heat transport fluid is conducted directly to the reservoir 11.

In further exemplary embodiments which are not illustrated here, two consumers are provided which are each arranged in one of the two outflow lines 14, 15, wherein one of the two consumers is intended to be cooled and the other heated. Instead of conducting the heated heat transport fluid directly to the reservoir 11, said heat transport fluid flows through the other consumer to be heated and outputs its heat there before being conducted further to the reservoir 11. The cooled heat transport fluid furthermore flows through the consumer 17 to be cooled and is conducted to the reservoir 11. 

1. A heat exchanger configured to surround a fluid line that guides a heat transport fluid, the heat exchanger comprising: at least one elastocaloric element configured to be connected to or arranged on the fluid line; at least one actuator operatively connected to the elastocaloric element and configured such that, when actuated, the at least one actuator exerts a force on the at least one elastocaloric element so as to deform the at least one elastocaloric element; and at least one fastening element configured to fasten the heat exchanger to the fluid line.
 2. The heat exchanger according to claim 1, wherein: the at least one actuator includes two actuators arranged on one elastocaloric element of the at least one elastocaloric elements in a longitudinal direction of the fluid line, and the two actuators are configured such that, when actuated, the two actuators exert the force on the one elastocaloric element so as to deform the one elastocaloric element.
 3. The heat exchanger according to claim 2, wherein each actuator of the two actuators is connected to and held by one fastening element of the at least one fastening element, the one fastening element arranged in the longitudinal direction of the fluid line.
 4. The heat exchanger according to claim 2, wherein the at least one actuator includes at least two actuators that divide a common fastening element of the at least one fastening element, and the at least two actuators are held by the common fastening element.
 5. The heat exchanger according to claim 1, wherein the at least one elastocaloric element, the at least one actuator, and the at least one fastening element are each designed in the form of an annular disk and configured to be arranged annularly around the fluid line.
 6. The heat exchanger according to claim 1, further comprising: a heat-conducting layer configured to thermally connect the at least one elastocaloric element to the fluid line.
 7. The heat exchanger according to claim 1, further comprising: a heat-insulating layer that thermally insulates at least the at least one actuator from the at least one elastocaloric element and from the fluid line.
 8. A heat exchange system, comprising: a fluid line; at least one heat exchanger comprising: at least one elastocaloric element connected to or arranged on the fluid line; at least one actuator operatively connected to the elastocaloric element and configured such that, when actuated, the at least one actuator exerts a force on the at least one elastocaloric element so as to deform the at least one elastocaloric element; and at least one fastening element that fastens the heat exchanger to the fluid line; and an electronic control unit configured to control the at least one actuator of the at least one heat exchanger.
 9. The heat exchange system according to claim 8, wherein: the at least one heat exchanger includes a plurality of heat exchangers arranged on the fluid line, and the electronic control unit is configured to control the at least one actuator of each of the plurality of heat exchangers.
 10. The heat exchange system according to claim 9, wherein the plurality of heat exchangers are connected to one another in the manner of a cascade.
 11. The heat exchange system according to claim 9, wherein the electronic control unit is configured to control the at least one actuator of the plurality of heat exchangers successively in time depending on flow properties of a heat transport fluid in the fluid line.
 12. The heat exchange system according to claim 8, further comprising: a reservoir that supplies heat transport fluid to the fluid line; and at least one return line through which heat transport fluid is guided out of the fluid line to the reservoir.
 13. The heat exchange system according to claim 8, further comprising: at least one internal return line which connects an end of the fluid line to a beginning of the fluid line, wherein the at least one heat exchanger is arranged between the beginning of the fluid line and the end of the fluid line.
 14. The heat exchange system according to claim 8, further comprising: at least one first valve arranged at a beginning of the fluid line; and at least one second valve arranged at an end of the fluid line. 